Pneumatic rubber tires, whether of the tube or tubeless type, are commonly mounted on rim structures which, in turn, are bolted or otherwise fastened to a rotatable hub. When employed in conjunction with passenger cars, or the like, the bead structure of the tires is sufficiently flexible so as to be distorted and mounted over the flanged part of a unitary structure rim. However, in larger vehicles, such as trucks and earthmoving equipment, the tire beads are very stiff and would require massive equipment to install them over the sidewall flange part of the rims without causing damage to the bead structure. Drop center rims have been made for large earth moving tires, but have not presently met with success or acceptance. Therefore, in such cases, the rims are constructed of at least one removable sidewall flange for facilitating the mounting and the demounting of a tire therefrom.
A rim having a removable sidewall flange and of the type especially adapted for use with heavy duty equipment is disclosed in U.S. Pat. No. 4,721,142, by Foster. The rim structure of the noted patent greatly facilitates the mounting and demounting of tires thereon. However, certain structures of the rim experience extremely high bending forces during road use and thus are susceptible to the development of cracks. This can be appreciated, in view that vehicles employing such type of rims can carry in excess of 200 ton loads.
More particularly, rims having a removable sidewall flange often include a gutter band ring with a groove into which a lock ring is locked to thereby fasten the sidewall flange with respect to the rim. The manner in which the gutter band portion of the rim is supported with respect to the hub subjects the gutter band to large bending forces, often resulting in cracking of the gutter band in the annular lock ring groove. The gutter band is generally not supported on its bottom surface thereof, under the outer annular groove in which a locking ring is locked. Thus, the lateral forces exerted by the sidewall rim structures on the lock ring exert a corresponding lateral force on the gutter band groove, thereby weakening the gutter band adjacent the groove, fatiguing it, and eventually cracking such structure.
The danger attendant with a crack in the gutter band is manifest during removal of the rim by repair personnel or workmen. During removal of the rim of the type noted, mounting wedges which wedge the rim onto a hub are removed from the hub, thereby allowing the lateral tire pressure to completely split the gutter band. In such an event, the tire pressure is either explosively discharged, or other parts of the rim can break, whereupon the rim and tire is essentially explosively blown off the vehicle. In either case, the danger to workmen removing such types of tires is great, and injuries can be fatal.
The foregoing problem has been addressed to a certain extent by the rim structure disclosed in U.S. Pat. No. 4,530,387 by Osawa. Disclosed in such patent is a dual taper rim structure which provides support for the gutter band groove and reduces the likelihood of cracking. However, such rim structure is especially adapted for single rim hubs, and thus does not provide a solution or remedy for vehicles utilizing dual rims. It can be appreciated that dual rim wheel assemblies are utilized on vehicles carrying extremely large loads, which situations create rim stresses and forces more likely to cause cracking of the components of the rim assembly.
From the foregoing, it can be seen that a need exists for an improved dual rim structure having rims with removable sidewall flanges, and of the type in which gutter band cracking is substantially reduced or eliminated. Another need exists for an improved dual rim structure which is readily adaptable to existing rim structures, and which reduces large bending stresses imposed thereon by heavy loads.